BCSC Pediactrics (Strabismus Terminology)

Question 1

What Greek word is strabismus derived from and what does this mean?

Answer 1

Starbismos which means “to squint, to look obliquely or askance.”

Question 2

Define strabismus.

Answer 2

Ocular misalignment (of any cause or type)

Question 3

Define orthophoria. What term is used synonymously with orthophoria.

Answer 3

Orthophoria is the ideal condition of ocular alignment under binocular conditions.

Question 4

Define heterophoria (or phoria).

Answer 4

Is an ocular deviation kept latent by the fusional mechanism.

Question 5

Define heterotropia (or tropia).

Answer 5

Is an ocular deviation that is manifest and not kept under control by the fusional mechanism.

Question 6

What is meant by the term latent strabismus?

Answer 6

Phoria

Question 7

What is meant by the term manifest strabismus?

Answer 7

Tropia

Question 8

Is orthophoria commonly seen in reality?

Answer 8

No. Most individuals have a slight exodeviation of both eyes which is overcome by fusional mechanisms. This exodeviation is therefore only evident during an EUA.

Question 9

A esotropia or esophoria are both types of ________ strabismus? Why?

Answer 9

convergent strabismus. Because the visual axes converges at a point closer than the fixation target.

Question 10

A exotropia or exophoria are both types of ________ strabismus? Why?

Answer 10

divergent strabismus. Because the visual axes converges at a point farther than the fixation target.

Question 11

A hypertropia or hyperphoria are both types of ________ strabismus? In which direction (superiorly or inferiorly) is the cornea rotated? In which direction (superiorly or inferiorly) is the fovea rotated?

Answer 11

vertical strabismus. The cornea rotated superiorly while the fovea rotates inferiorly

Question 12

A hypotropia or hypophoria are both types of ________ strabismus? In which direction (superiorly or inferiorly) is the cornea rotated? In which direction (superiorly or inferiorly) is the fovea rotated?

Answer 12

vertical strabismus. The cornea rotated inferiorly while the fovea rotates superiorly

Question 13

Incyclotropia or incyclophoria are also known as ____ strabismus?

Answer 13

Intorsional

Question 14

Excyclotropia or excyclophoria are also known as ____ strabismus?

Answer 14

Extorsional

Question 15

Is fusional control always present in a phoria?

Answer 15

Yes. Any ocular deviation is corrected by the fusional mechanism (to prevent diplopia). If fusional control was temporally lost it would become an intermittent tropia.

Question 16

Define a intermittent tropia.

Answer 16

A ocular deviation in which fusional control is present part of the time. Therefore, the eyes are only aligned some of the time under binocular conditions.

Question 17

Define tropia.

Answer 17

A ocular deviation in which fusional control is not present. Therefore, the eyes are not aligned under binocular conditions.

Question 18

Define a comitant (concomitant) strabismus.

Answer 18

The size of the ocular deviation does not vary by more than seven prism diopters with direction of gaze or with the eye used for fixating.

Question 19

Define a incomitant (noncomitant) strabismus.

Answer 19

The size of the ocular deviation varies by more than seven prism diopters with direction of gaze or with the eye used for fixating.

Question 20

A patient’s ocular deviation increases significantly when he alternates fixation between eyes. This is a form of _______ strabismus?

Answer 20

incomitant or noncomitant

Question 21

A patient’s ocular deviation changes significantly with changes in his diretion of gaze. This is a form of _______ strabismus?

Answer 21

incomitant or noncomitant

Question 22

A patient’s ocular deviation changes by a couple of prism diopters with changes in his diretion of gaze. This is a _______ strabismus?

Answer 22

comitant or concomitant

Question 23

What are the two types of fixation? Define them.

Answer 23

Alternating fixation means there is spontaneous alternation of fixation from one eye to the other. Monocular fixation means there is a definite preference for fixation with one eye.

Question 24

Define a congenital strabismus?

Answer 24

An ocular deviation present before 6 months, presumably related to a defect at birth.

Question 25

Define a acquired strabismus?

Answer 25

An ocular deviation with onset later than 6 months, presumably with a period of apparently normal visual development.

Question 26

What types of deviations are considered horizontal deviations?

Answer 26

Esodeviation or exodeviation

Question 27

What types of deviations are considered vertical deviations?

Answer 27

Hyperdeviation or hypodeviation

Question 28

What types of deviations are considered torsional deviations?

Answer 28

Incyclodeviation or excyclodeviation

Question 29

Can a patient have multiple types of ocular deviation at one time?

Answer 29

Yes. This is referred to as combined deviation.

Question 30

The abbreviations E, ET, and E(T) refer to what types of strabismus?

Answer 30

Esophoria, esotropia, and intermittent esotropia respectively.

Question 31

The abbreviations X, XT, and X(T) refer to what types of strabismus?

Answer 31

Exophoria, exotropia, and intermittent exotropia respectively.

Question 32

The abbreviations RH, RHT, and RH(T) refer to what types of strabismus?

Answer 32

Right hyperphoria, right hypertropia, and intermittent right hypertropia respectively.

Question 33

The abbreviations LH, LHT, LH(T) refer to what types of strabismus?

Answer 33

Left hyperphoria, left hypertropia, and intermittent left hypertropia respectively.

Question 34

The abbreviations RhoT and LhoT refer to what types of strabismus?

Answer 34

Right hypotropia and left hypotropia respectively.

Question 35

The abbreviations O and Ex=O refer to what types of strabismus?

Answer 35

Orthophoria (orthotropia)

Question 36

What is indicated by the addition of a (') to any of the strabismus abbreviations?

Answer 36

The strabismus is present at near (e.g. E(T)' indicates a intermittent esotropia at near).

Question 37

Is a strabismus always present at both near and distance.

Answer 37

No. This is why you must perform and document ocular alignment testing at both near and distance. Therefore, a normal exam at near and distance would be document: Ortho, Ortho'

Question 38

What is the optical axis?

Answer 38

The line that best approximates the line passing through the optical center of the cornea, lens, and fovea.

Question 39

What is the pupillary axis?

Answer 39

The imaginary line perpendicular to the corneal surface and passing through the midpoint of the entrance pupil.

Question 40

What is the visual axis?

Answer 40

The imaginary line connecting the fixation point and the fovea.

Question 41

Does the textbook definition of an optical axis exist in the eye? Why or why not?

Answer 41

No. The textbook optical axis does not exist in the eye because the lens is slightly decentered with respect to the cornea and the visual axis. Therefore, the best approximation of this line is taken to be the optical axis.